1. Field of the Invention
The invention relates generally to devices and methods for providing a watercraft transom having an adjustable height feature allowing optimal matching with the drive shaft of the watercraft's motor.
2. Description of the Related Art
Outboard watercraft motors are generally available in either a short, long or extra long drive shaft version as further described herein.
As used herein, a short drive shaft outboard may be approximately 15 inches in length. These short drive shafts may be found in use in, e.g. small boats, sailboats with movable brackets, small sailboats, inflatable boats and canoes. These short drive shafts may comprise the primary motor or be used as a trolling motor or other non-primary motor. Generally, the watercraft making use of the short drive shaft outboard motors comprise an aft transom that is approximately 15 to 17 inches in height.
Long drive shafts, as that term is used herein, for available outboard motors may comprise a drive shaft that is approximately 20 inches in length. Such long drive shaft outboard motors may be found in use with, without limitation, sailboats, and pontoons. The watercraft using the 20-inch long drive shaft outboard motors generally comprise an aft transom that is approximately 18 to 21 inches in height.
Finally, extra long drive shafts for available outdoor motors may comprise a drive shaft that is approximately 25 inches in length. Outboard motors comprising the long drive snail may be found in use with pontoons, catamarans, sailboats, large barges and other watercraft having a relatively high transom, i.e., wherein the transom is between 21 to 27 inches in height.
When a watercraft owner selects an outboard motor to match with the watercraft for optimal performance, it is critical to measure the watercraft's transom as well as the motor, specifically the drive shaft length, to make sure the motor will fit the watercraft's transom. With outboard motors, the most important measurement is the drive shaft length. Mismatching the outboard motor drive shaft length with the transom height can result in poor performance. For example, an outboard with a shaft length that is too short for the watercraft will cause the propeller to lift out of the water when the watercraft is on plane, compromising performance.
Outboard motor drive shafts are thus optimally individually fitted to a watercraft according to the boat's aft transom height. When a watercraft lifts under power and skims across the water, it performs and handles most efficiently when the propeller is the only engine part remaining in the water. For this reason, the shaft length must match the height of a watercraft's aft transom. This general and known concept is illustrated in FIG. 1. There the transom height T is indicated with an outboard motor having a matched, fixed non-adjustable drive shaft length S, wherein S≈T. Drive shaft length S is generally measured from the top of the transom to the cavitation plate. Transom height T is generally measured from the top to the bottom of the aft transom. Thus T is approximately equal to S in the optimal configuration of FIG. 1. Currently, however, this optimized match between transom height and outboard motor drive shaft length S is, unfortunately, not easily achieved in many cases.
Table 1 below illustrates some available combinations of transom height and the closest available outboard motor drive shaft length:
TABLE 1Typical Fixed Non-AdjustableCurrently Avilable OutboardTransom Height Ranges:Drive shaft Length:  14″-17.25″15″ Shaft (Short)17.25″-19.5″ No Optimal Match, must chooseeither 15″ or 20″19.5″-22.5″20″ Shaft (Long)22.5″-27″  25″ Shaft (Extra-Long)
Table 1 illustrates the basic problem: for many current applications, the transom height vs. drive shaft length is mismatched, resulting in sub-optimal watercraft performance.
To illustrate in terms of the state of the art, we refer now to the typical construction strategy on, e.g., a pontoon watercraft that is designed for use with an extra long drive shaft outboard motor, i.e., the drive shaft length is approximately 25 inches. This exemplary pontoon would optimally comprise an aft transom that is fixed at approximately 25 inches to provide optimal matching between drive shaft length and transom height. If, on the other hand, the exemplary pontoon watercraft is being designed for use with a long drive shaft outboard motor with a drive shaft, length of 20 inches, the fixed transom height will be designed to compensate with a height of approximately 20 inches to optimally match the drive shaft length and transom height. Thus, in both of these cases, S≈T as illustrated in exemplary FIG. 1.
In these known cases, the transom height is always fixed, i.e., not adjustable in height, and is manufactured to fit an outboard motor comprising a known and specified drive shaft length that is also always fixed. At times, the watercraft user may subsequently wish to switch from a short drive shaft outboard motor to a long drive shaft outboard motor, from a long to an extra long drive shaft, etc. In this event, the fixed, non-adjustable transom height is no longer optimal with adverse impact on the watercrafts performance. Currently, correction of this mismatching between the transom height T and new drive shaft length S requires modifying the transom height T to re-optimize its match with the length S of the new outboard motor's drive shaft. Modification of the transom height T requires cutting and fabrication of components to make the conversion and adjustment. Such conversion is difficult and expensive.
The present invention addresses these problems.